Plague is a highly infectious bacterial disease (Yersinia pestis) transmitted by fleas. It primarily affects rodents; however, humans and their pets (dogs and especially cats) can also contract plague.
This is the same disease that ravaged Europe in the 14th century - Black Death.
The Black Death was one of the most devastating pandemics in human history, peaking in Europe between 1348 and 1350. While there were several competing theories as to the etiology of the Black Death it has been conclusively proven via analysis of ancient DNA from plague victims in northern and southern Europe that the pathogen responsible is the Yersinia pestis bacteria. Thought to have started in China, it travelled along the Silk Road and reached the Crimea by 1346. From there it was probably carried by Oriental rat fleas living on the black rats that were regular passengers on merchant ships, it spread throughout the Mediterranean and Europe.
The Black Death is estimated to have killed 30–60 percent of Europe's population, reducing world population from an estimated 450 million to between 350 and 375 million in the 14th century. The aftermath of the plague created a series of religious, social and economic upheavals, which had profound effects on the course of European history. It took 150 years for Europe's population to recover.
Plague in humans is now relatively rare, but cases continue to occur.
Plague is successfully treated with antibiotics in the early stages, but correct early diagnosis is essential. Plague can quickly progress to the more serious stages (septicemic and pneumonic plague).
Because of the potential danger of pneumonic plague epidemics, Environmental Health staff place a high priority on prevention of human plague cases. You can minimize your exposure to plague by carefully following the precautions listed below.
Where is plague found?
Plague occurs in the foothills, plateaus, mountains and foggy coastal belt areas in California. Plague is absent from the southeastern desert region and the central valley.
Exposure to plague is possible throughout Ventura County. The major threat of plague to humans is in the rural and the suburban foothills of the county. Diseased animals have been detected in the Santa Monica mountains, foothills north of Fillmore, Ojai, Lockwood Valley and the Mt. Pinos-Frazier Mountain area.
Which animals carry plague?
The most important wild rodent reservoirs of plague are ground squirrels and chipmunks. Other rodents that carry plague are woodrats, mice, marmots and domestic rats. Plague is lethal to many rodents. Any sign of sick or dead rodents or a high flea population is a warning that plague may be in the area.
Domestic animals can acquire plague and pose a direct threat to humans. Dogs rarely become ill but cats are highly susceptible and can suffer severe illness and possible death.
What are the early symptoms?
In humans, plague goes through different stages:
Bubonic plague
The initial stage symptoms (bubonic plague) are fever chills, headache and muscle aches, feeling of weakness and usually swollen and tender lymph nodes, or buboes, especially under the arm pit. The usual incubation period is 2 to 10 days
Septicemic plague
In septicemic stage, the bacteria has moved into the blood stream. In this stage the buboes are inconspicuous. Septicemic (or septicaemic) plague is a deadly blood infection, one of the three main forms of plague. It is caused by Yersinia pestis, a gram-negative bacterium.
Like other forms of gram-negative sepsis, septicemic plague can cause disseminated intravascular coagulation, and is, without treatment, almost always fatal (the mortality rate in the medieval times was 99-100 percent). Septicemic plague is the rarest of the three plagues that struck Europe in 1348, the other forms are bubonic and pneumonic plague (see the section on septicemic plague in medieval times).
This disease is contracted usually through the bite of an infected rodent or insect, but can also be contracted through an opening in the skin or by cough from another infected human.
Pneumonic plague
In the pneumonic plague stage, the bacteria moves into the lungs and becomes airborne through normal respiration or when the patent sneezes or coughs. This is the most severe stage progressing rapidly and has a high death rate. This is also a common stage for the transmission from pets to their owners. A cat with plague will become very ill, it may stop eating and have a fever. Swollen lymph nodes may occur in the neck area.
How can I be exposed to Plague?
People can get the disease from animals in several ways.
The most important routes of transmission are:
- Pets
Infected rodent fleas can be brought into a home or campsite by dogs or cats, where the fleas then bite you. Plague pneumonia can be contracted from a sick cat that is coughing or sneezing. - Bites of Fleas from Infected Rodents
Fleas will leave a sick or dead rodent and can bite people or their pets. - Direct Contact with Sick Animals
The bacteria in the blood, urine or saliva of an infected animal can enter cuts or abrasions in the hands.
What should I do if I live in or visit a plague area?
- General precautions
Contact a physician immediately if you become ill within 7 days of being in a plague area. Inform your doctor where you have been and what possible exposure that you may have had.
Use precaution when handling a sick pet that has been in a plague area.
Avoid face to face contact with the sick animals. Inform a veterinarian that the sick pet has been in a plague area. Avoid all contact with rodents and their fleas.
Do not touch sick or dead rodents. Report them to rangers or health authorities. - Where you live
Keep rodent populations down around the home or other inhabited areas. Exclude them from entering buildings.
Eliminate access of the rodents to food or shelter.
Minimize pet contact with rodents and their fleas.
Treat pets with flea powder on a regular basis.
Flea collars may work too slowly to be of benefit. - Where you work or play
Do not camp, sleep or rest near animal burrows.
Do not feed rodents in the campgrounds or picnic areas.
Store food and refuse in rodent proof containers.
Wearing long pants tucked into boot tops or socks may reduce your exposure to fleas.
Insect repellents sprayed on socks and pants may also help. - Leave pets at home:
If you must bring pets, keep them on a leash or confined away from any rodent activity.
Do not allow your pets to approach sick or dead rodents or to explore rodent burrows.
Protect pets with flea powder. - Hunters:
Use rubber gloves when skinning or cleaning animals. Cook these animals thoroughly. Clean any utensils thoroughly.
What is the role of the Environmental Health Division?
The Environmental Health Division staff monitors plague activity throughout the county. Rangers, park personnel and others are also trained to watch for sick or dead rodents or other evidence that plague may be active in a particular area. They are also encouraged to report their findings to the Environmental Health Division or the California Department of Public Health.
Preventive measures will be instituted when animal plague is found in areas where human exposure is possible. Warning signs will be posted and after careful evaluation the area may be quarantined.
Insecticide dust is applied into rodent burrows or into bait stations (tube like containers). Rodents that enter the bait station pick up the insecticide dust in their fur killing the fleas. The dust is also taken back to the nest in their fur killing the fleas in the nest. This method of flea control is very effective. It minimizes the amount of insecticide used and does not harm the rodents.
If you see bait stations or rodent traps-Please do not disturb them.